harrow

harrow, farm implement, consisting of a wooden or metal framework bearing metal disks, teeth, or sharp projecting points, called tines, which is dragged over plowed land to pulverize the clods of earth and level the soil. Harrows are also used to uproot weeds, aerate the soil, and cover seeds. Primitive harrows were twiggy branches drawn over the soil to smooth it; in India a ladderlike device of bamboo is still used. In modern large-scale farming, harrows are of varied types. Some are simply dragged behind a tractor or draft animal; some are suspended on wheels; many have levers to adjust the depth of the cut. There may be one or more gangs (sets) of cutting parts per harrow, and one or more harrows may be drawn at a time. In disk harrows, which next to the plow are the most widely used tillage implements, the saucer-shaped disks are set at angles to the line of pull for maximum pulverization. Spike-tooth harrows have rigid teeth, and spring-tooth harrows have curved tines that adjust to obstacles. The rotary crossharrow has power-driven rotating toothed disks; another type of harrow slices through topsoil and vegetation with curved knives. In general, the harrow is similar to the cultivator, except that it penetrates the soil to a lesser depth.